This invention relates to a fabric length measuring device and more particularly to a device for measuring the length of a fabric workpiece as it is sewn by a sewing machine.
During a fabric sewing operation it is sometimes desirable to measure the length of the fabric workpiece which is sewn. When a sewing machine is operated at a relatively low speed, this could possibly have been done by mechanical counters such as that disclosed in U.S. Pat. No. 1,468,145 (Entriken). With the advent of high speed, commercial sewing machines, however, such mechanical measuring devices are not suitable. In a present day commercial sewing machine the fabric workpiece is accelerated and decelerated by the feed dogs at rates as high as 7,000 times per minute, moving in increments of one tenth to one seventh of an inch at a time. Mechanical prior art counters have inertial constraints and torque requirements which can not meet these specifications. Furthermore, the material subsequent to a stitch in the area behind the needle, while relaxing during deceleration, literally moves backwards to some extent. With some prior art counters this has the effect of adding to the measurement which is being made; producing an inaccurate count.